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Full text of "The manufacture and properties of iron and steel"

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HEAT  TREATMENT.
277
showed an increase in only three cases, the maximum being 2.81 per cent., and a decrease in five cases, the greatest loss being 7.20 per cent.
The elastic limit fell much more than the ultimate strength, and here again the Bessemer seems to be different from the open-hearth steel, for while the elastic ratio of the former is lowered from 2.1 to 4.7 per cent, by annealing, the latter loses from 7.2 to 11.9 per cent. It will not do to draw a general conclusion from these limited data on the nature of the two kinds of steel, but whether
TABLE XV-C.
Comparison of the Natural and Annealed Open-Hearth Steel Bars Given in Table XV-A, which show about the same Ultimate Strength.
rd'as o-d flfl ? a M H-U	'          ft	Limits of ultimate Strength in group ; pounds per square inch.	Number of heats in average.	Condition of bar.	Ultimate strength; pounds per square inch.	Elastic limit; pounds per square inch.	. Elongation in 8 inches ; per cent.	Reduction of area; per cent.	"i _o . S
	I	56000 to 60000	4 7	Natural . Annealed	58568 68864	40800 85120	29.69 28.61	60.78 63.47	68.81 60.17
	n	68000 to 72000	2 12	Natural Annealed	70580 69402	49000 40505	26.88 28.04	61.10 56.54	69.47 58.36
	in	55000 to 60000	4 7	Natural Annealed	58180 55021	40400 81576	80.18 80.86	61.75 60.00	69.51 57.39
	IV	60000 to 64000	-.   7 2	Natural Annealed	62089 60850	42441 84000	80.14 26.50	60.86 52.10	68.36 55.87
	y	66000 to 70000	2 12	Natural . Annealed	69420' 67618	45090 89408	25.68' 26.81	59.80 51.86	64.96 58.27
further experiment would or would not corroborate these results, it is quite certain that annealing under ordinary conditions, even though very carefully conducted, may produce grave differences in physical properties in steels of similar composition which have been rolled in the same manner and treated at the same time, even. When the effect upon the ultimate strength has been the same.
It Would also appear that in the Bessemer steel the marked increase in ductility is purchased at a great sacrifice of strength, and the question arises whether the gain is not more than balanced by'theloss, and whether an equal degree of toughness could not be